Aquaculture: An ecological Pandora's Box?

WITH human population growth showing no signs of slowing, many people -- ordinary citizens as well as decision makers -- have begun to wonder how we shall feed the future.

One response that always seems to generate enthusiasm is fish farming, or aquaculture.

On the surface, it is easy to see why this age-old industry might offer practical cures to current dilemmas. With world fisheries exploited at unsustainable levels, and world protein demand on the rise, aquaculture holds the promise of feeding vast numbers of people with relatively small inputs of energy and capital. Unlike many other domesticated animals, farmed fish might live in a virtually "closed" system, requiring little land and, at least theoretically, only organic waste materials as food. Some farms I have seen in the tropics are little more than back-yard ponds, with fish raised on kitchen scraps.

This "cottage" character of fish farming appeals to many proponents, especially development agencies, because hardly any infrastructure is required, and fish farmers rapidly become self-sufficient. This makes aquaculture a popular fix in the developing world. During the recent Cousteau expedition to the Mekong River in Southeast Asia, I was struck by the booming aquaculture business in Vietnam. Here, families live in floating houses on the river. Above, meals are cooked, games are played, business is transacted. Below, a caged basement contains vast numbers of fish. The basement is a living garbage disposal that also serves as a source of fish for the next meal.

Some farmed fish, such as tilapia, are raised industrially in the wealthier nations, and end up on the tables of the finest restaurants, an economic world apart from the humid ponds of their cousins in Africa and Asia. Aquaculture would seen to incarnate the principle of "sustainable development": conserving natural resources while generating income.

Yet evidence is mounting that fish farming is being conducted in ways that are more damaging than beneficial to the environment and local economies.

In many instances, such as salmon farming, local empowerment is not the goal. Salmon farms are run by international companies with little regard for the health of the local ecosystem they are invading.

Far from complementing local fisheries, salmon farms compete with and destroy their sister industry. In the northern nations, farmed salmon escape in vast numbers and compete with wild fish for food, often eating wild fish larvae. They still belong to their breeders, and thus may not be caught by fishermen. Meanwhile, native wild fish stocks collapse.

Salmon farming is only profitable if the fish are packed tightly in rearing pens. Usually, the fish are unable to even move about. Bacteria also profit from this arrangement, and spread rapidly throughout entire farms. Because these fish are not completely isolated from their environment, they pass on their diseases to healthy wild fish. Salmon farms have been linked to the appearance of new and deadly bacteriological epidemics among wild salmon in the United Kingdom, Norway and the United States.

The most common method of fighting diseases is with antibiotics, such as penicillin and oxytetracyclines. Research has demonstrated that these are passed directly through the fish into the environment, lodging in wild fish, shellfish and crustaceans, moving up the food chain in concentrations dangerous to the ultimate consumers: humans.

In addition, antibiotics only call forth newer, hardier strains of the disease they were intended to combat, may of which are now essentially drug resistant.

Such practices affect more than just wild salmon. Waste streams from salmon farms can be substantial enough to create "dying zones" in the waterways where they are situated. Smothered by tons of organic wastes, commercially valuable species such as prawns have been eradicated in locations shared with salmon farms. Wild fisheries are depleted at the same time that huge numbers of farmed fish hit the market. Prices fall, jobs are lost, local economies are shattered.

In Norway and Ireland, coastal residents have successfully lobbied their governments to enact restrictions on salmon farming. The large, international aquaculture companies simply move on to newer, less regulated pastures. Because the business is new, not all of these unfortunates are in the developing world.

Alexandra Morton lives in Broughton Archipelago, a rugged maze of inlets on the coast of British Columbia, Canada. She is a marine biologist who has studied orcas, using photo-identification to compare the behavior of transient and resident populations. Today, she spends much of her time analyzing the behavior of the most recent transient residents of her home waters: fish farmers.